PotD protein stimulates biofilm formation by Escherichia coli

In natural environments bacteria often adopt a biofilm-growth mode. PotD is a spermidine/putrescine-binding periplasmic protein belonging to polyamine transport system and we have examined its role during biofilm formation and for planktonic growth in Escherichia coli BL21(DE3) strains that either over-express PotD (PotD+), or under-express it (PotDi) and also in a control strain with vector pET26b(+) (PotD0). The three strains displayed similar growth in planktonic growth-mode, but over expression of PotD protein greatly stimulated the formation of biofilms, while less biofilm formed by strain PotDi in comparison to strain PotD0. The expressions of five genes, recA, sfiA, groEL, groES, and gyrA, were increasingly expressed in PotD+ biofilm cells. Thus, PotD is likely to change the rate of polyamine synthesis, which stimulates the expression of SOS genes and biofilm formation.     

Catabolite repression of Escherichia coli biofilm formation

Biofilm formation was repressed by glucose in several species of Enterobacteriaceae. In Escherichia coli, this effect was mediated at least in part by cyclic AMP (cAMP)-cAMP receptor protein. A temporal role for cAMP in biofilm development was indicated by the finding that glucose addition after approximately 24 h failed to repress and generally activated biofilm formation.     

L-Tryptophan prevents Escherichia coli biofilm formation and triggers biofilm degradation

The effect of deletion of trp operon and tna operon on the Escherichia coli biofilm formation was investigated in order to elucidate the role of L-tryptophan metabolism in biofilm formation. trp operon deletion mutants ΔtrpC, ΔtrpD and ΔtrpE deficient in L-tryptophan biosynthesis showed higher biofilm formation. In addition, ΔtnaC with increased L-tryptophan degradation activity showed higher biofilm formation. On the contrary, ΔtnaA deletion mutant which lost L-tryptophan degradation activity showed low biofilm formation. From these results, it was suggested that decrease of intracellular L-tryptophan level induced biofilm formation and increase of L-tryptophan repressed biofilm formation. So the effect of the addition of L-tryptophan to the medium on the E. coli biofilm formation was investigated. L-Tryptophan addition at starting culture decreased biofilm formation and furthermore L-tryptophan addition after 16 h culture induced the degradation of preformed biofilm. From the above results, it was suggested that maintenance of high intracellular L-tryptophan concentration prevents E. coli biofilm formation and elevation of intracellular L-tryptophan concentration triggers degradation of matured biofilm.     

The influence of nonconjugative Escherichia coli plasmids on biofilm formation and resistance

Aims: This work describes the effects of the presence of nonconjugative plasmids in Escherichia coli cells forming biofilms on a flow cell system under turbulent conditions. Methods and Results: The pET28 and pUC8 plasmids were separately used to transform E. coli JM109(DE3). Biofilm formation, removal and antimicrobial susceptibility to the cationic biocide benzyldimethyldodecylammonium chloride (BDMDAC) were assessed. Transformed cells formed thicker biofilms with higher cell densities, and the metabolic activity was higher whereas nontransformed cells had higher viabilities. Biocide treatment was not efficient for biofilm removal but was effective for cell killing. Biofilms formed by nontransformed cells were less affected by the treatment. Conclusions: Cell transformation with the tested plasmids has significant impacts on biofilm formation, cell viability, metabolic activity and resistance to biocide treatment. Our results show that in biofilm studies involving deletion/complementation experiments, a control with the strain carrying a plasmid devoid of the gene under investigation must be included so that the real effects of the genetic manipulation are not biased by the presence of the plasmid backbone. Significance and Impact of the Study: This is the first report where the presence of nonconjugative plasmids is assessed in flow conditions analysing biofilm formation, removal and antimicrobial susceptibility of high cell‐density biofilms.     

Structure of the Escherichia coli S10 ribosomal protein operon.

The complete structure of the Escherichia coli S10 ribosomal protein operon is presented. Based on the DNA sequence, the deduced order of the 11 genes in the operon is rpsJ, rplC, rplD, rplW, rplB, rpsS, rplV, rpsC, rplP, rpmC, rpsQ. The estimated transcribed length of the operon is 5181 base pairs. Putative sequences involved in ribosome binding are discussed. The DNA sequence data corrects several errors in previously determined protein sequence data.     

The response of Escherichia coli biofilm to salicylic acid

In this research, salicylic acid is proposed as an alternative biocide-free agent suitable for a preventive or integrative anti-biofilm approach. Salicylic acid has been proved to: (1) reduce bacterial adhesion up to 68.1 ± 5.6%; (2) affect biofilm structural development, reducing viable biomass by 97.0 ± 0.7% and extracellular proteins and polysaccharides by 83.9 ± 2.5% and 49.5 ± 5.5% respectively; and (3) promote biofilm detachment 3.4 ± 0.6-fold. Moreover, salicylic acid treated biofilm showed an increased amount of intracellular (2.3 ± 0.2-fold) and extracellular (2.1 ± 0.3-fold) reactive oxygen species, and resulted in increased production of the quorum sensing signal indole (7.6 ± 1.4-fold). For the first time, experiments revealed that salicylic acid interacts with proteins that play a role in quorum sensing, reactive oxygen species accumulation, motility, extracellular polymeric matrix components, transport and metabolism.     

Inhibition of enteropathogenic Escherichia coli biofilm formation by DNA aptamer

Molecular Biology Reports - Enteropathogenic Escherichia coli (EPEC) is a bioagent that causes diarrhea through the formation of biofilm. The recalcitrant of EPEC to the current conventional...